88 0. P. MARSHALL. 



or transverse striation. The muscle treated with osmic acid 

 shows faint fibrillation, but no distinct fibrils. 



Patella. — The Limpet was chosen for an investigation of 

 the structure of the heart muscle. In gold preparations of 

 the ventricle I find the network of striped muscle present 

 (fig. 5). 



In the heart of the Anodon I could not determine with cer- 

 tainty whether the network was present or not, although faint 

 indications of it were obtained. 



Ostrea. — The adductor muscle of the Oyster consists of two 

 portions : a white opaque portion, and a more gelatinous por- 

 tion. Gold preparations were made of each of these. The cells 

 of the " white muscle " are large, with clear outlines, and re- 

 markable for the clearness and transparency of their proto- 

 plasm. The cells of the " gelatinous muscle " are smaller 

 and less transparent. Neither of these showed any network or 

 fibrillation. 



Helix pomatia. — Gold preparations of the muscle of the 

 foot show that it consists of very small cells of the unstriped 

 type densely massed together. 



The muscle of the odontophore, however, shows transverse 

 striation, which under the high power is seen to be caused by 

 the presence of the typical network of striped muscle. 



Pec ten. — The Pecten differs from most of its class by per- 

 forming rapid movements of its adductor muscle whereby it 

 propels itself through the water. Gold preparations of the 

 adductor muscle made by my friend Mr. J. T. Cunningham 

 show the network of striped muscle very plainly (fig. 4). I 

 have not observed the double oblique striation described by 

 Schwalbe in the muscle of Molluscs and Echinoderms. As 

 this is not seen in gold and osmic acid preparations, I think it 

 must be an optical effect. Schwalbe, indeed, admits that in 

 Ophiothrix the transverse striation is due to folds in the 

 sarcolemma (loc. cit., p. 211). 



